A bedridden elderly person or patient cannot roll over as one wishes and mostly sleeps in the same position for a long time. Then, a portion where a bone projects and the body weight is concentrated is pressured, thus causing bad blood circulation and developing bedsores (pressure ulcers). To prevent bedsores, it is necessary to change body positions periodically to distribute the body pressure. It is a substantial burden, however, for a caregiver or nurse to change the body position of the bed-ridden elderly person or patient. It is thus difficult to rely solely on manpower for prevention of bedsores.
A variety of apparatuses have been proposed to prevent bedsores without manpower. For instance, Patent Literatures 1 and 2 each disclose a bedsore preventing apparatus having a mattress including a plurality of air bags, a pressure sensor corresponding to each of the air bags, and an air volume adjuster adjusting an air volume of the air bags. Furthermore, Patent Literature 3 discloses a mattress having a seat being a collection of a plurality of cells, a sensor disposed in each of the cells to detect a bedsore portion, and a controller adjusting an internal pressure of the cells.